Calcite - Logical Plan (Logical algebra)

About

Sql Engine - Logical Plan (Query) in Calcite

A logical plan is a relational expression with only logical operator. Logical algebra has no implementation of the relational operator and therefore can't run.

The logical plan is the first plan created when transforming a Sql tree into relational algebra.

All logical operator starts with the prefix Logical

Management

Create

Every logical plan is created from a SQL tree (sqlNode)

The main entry point is the sqlToRelConverter but you would generally use a tool to call it such as the planner

not the same that the planner optimizer)

Planner

Extract from the getting started page with the query processing tool

RelRoot relRoot = planner.rel(sqlNodeValidated);

sqlToRelConverter

With the sqlToRelConverter org/apache/calcite/prepare/Prepare

RelRoot root = sqlToRelConverter.convertQuery(sqlQuery, needsValidation, true);

Print

As a logical plan is just a relational expression, you just need to print it (explain):

Example: All logical operator starts with the prefix Logical

4:LogicalProject(name=[$2])
  3:LogicalFilter(condition=[=($0, 100)])
    2:LogicalJoin(condition=[=($1, $5)], joinType=[inner])
      0:LogicalTableScan(table=[[HR, emps]])
      1:LogicalTableScan(table=[[HR, depts]])

This is equivalent to the below SQL:

select * 
from emps inner join depts on deptno
where empid = 100

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